Memory difficulties are a prominent feature of normal human aging, and especially of Dementia of the Alzheimer's Type (DAT). There is, however, evidence that one type of memory, semantic memory, may be relatively unaffected by normal aging. Semantic memory consists of knowledge of semantic concepts and verbal symbols, and the rules for their usage. While some studies have reported semantic memory deficits in DAT, the tasks used made heavy demands on attentional capacity, and thus, may not accurately reflect the state of semantic memory structure and function in demented persons. The studies in the present application will examine similarities and differences in the semantic memory abilities of normal young, normal elderly and demented elderly persons. The tasks will employ the theoretical constructs and methodology of cognitive psychology and are designed to involve "automatic" processes that make minimal demands upon attentional capacity (e.g., semantic priming tasks). Information gained in these studies should help characterize the effects that dementia and normal aging have on various aspects of semantic memory. Any differences in the effect of normal and abnormal (i.e., Alzheimer's disease) aging on semantic memory would be helpful in differential diagnosis. If, however, semantic memory is resistant to the general cognitive deterioration seen in DAT, then in the future, measurements of semantic memory performance could serve as a useful indicator of premorbid cognitive abilities, as well as a benchmark against which to evaluate cognitive decline or improvement (e.g., with pharmacological treatment) over time.